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| Titel |
Impacts of urban land-surface forcing on ozone air quality in the Seoul metropolitan area |
| VerfasserIn |
Y.-H. Ryu, J.-J. Baik, K.-H. Kwak, S. Kim, N. Moon |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 4 ; Nr. 13, no. 4 (2013-02-25), S.2177-2194 |
| Datensatznummer |
250018431
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| Publikation (Nr.) |
 copernicus.org/acp-13-2177-2013.pdf |
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| Zusammenfassung |
| Modified local meteorology owing to heterogeneities in the urban–rural
surface can affect urban air quality. In this study, the impacts of urban
land-surface forcing on ozone air quality during a high ozone (O3)
episode in the Seoul metropolitan area, South Korea, are investigated using
a high-resolution chemical transport model (CMAQ). Under fair weather
conditions, the temperature excess (urban heat island) significantly modifies
boundary layer characteristics/structures and local circulations. The
modified boundary layer and local circulations result in an increase in
O3 levels in the urban area of 16 ppb in the nighttime and 13 ppb in
the daytime. Enhanced turbulence in the deep urban boundary layer dilutes
pollutants such as NOx, and this contributes to the elevated O3
levels through the reduced O3 destruction by NO in the NOx-rich
environment. The advection of O3 precursors over the mountains near
Seoul by the prevailing valley-breeze circulation in the mid- to late
morning results in the build-up of O3 over the mountains in conjunction
with biogenic volatile organic compound (BVOC) emissions there. As the
prevailing local circulation in the afternoon changes to urban-breeze
circulation, the O3-rich air masses over the mountains are advected
over the urban area. The urban-breeze circulation exerts significant
influences on not only the advection of O3 but also the chemical
production of O3 under the circumstances in which both anthropogenic
and biogenic (natural) emissions play important roles in O3 formation.
As the air masses that are characterized by low NOx and high BVOC
levels and long OH chain length are advected over the urban area from the
surroundings, the ozone production efficiency increases in the urban area.
The relatively strong vertical mixing in the urban boundary layer embedded
in the sea-breeze inflow layer reduces NOx levels, thus contributing to
the elevated O3 levels in the urban area. |
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